Time sharing in working memory processing.

Although working memory (WM) is usually defined as a cognitive system coordinating processing and storage in the short term, in most WM models, memory aspects have been developed more fully than processing systems, and many studies of WM tasks have tended to focus on memory performance. The present study investigated WM functioning without focusing exclusively on short-term memory performance by presenting participants with an n-back task on letters, n varying from 0 to 2, each letter being followed by a tone discrimination task involving from one to three tones. Predictions regarding the reciprocal effects of these tasks on each other were motivated by the time-based resource-sharing (TBRS) theoretical framework for WM that assumes the temporal sharing of attention between processing and memory. Although, as predicted, increasing the n value had a detrimental effect on tone discrimination in terms of accuracy and response times, and increasing the number of tones disrupted speed and accuracy on n-back performance, the overall pattern of results did not perfectly fit the TBRS predictions. Nonetheless, the main alternative models of WM do not seem to offer a complete account. The present findings point toward the need to use a larger range of tasks and situations in designing and testing models of WM. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Process intensification of synthesis of metal organic framework particles assisted by ultrasound irradiation.

This study synthesized UiO-66, a typical Zr-Metal Organic Framework (MOF), by using an ultrasound-assisted synthesis method to reduce the synthesis time. This method was short-time ultrasound irradiation at the initial stage of the reaction. As compared with average particle size of conventional solvothermal method (=192 nm), averaged particle size by the ultrasound-assisted synthesis method showed particle sizes that were smaller on average, ranging from 56 to 155 nm. In order to compare the relative reaction rates of the solvothermal method and the ultrasound-assisted synthesis method, the cloudiness of the reaction solution in the reactor was observed with a video camera, and the luminance was calculated from the images obtained by the video camera. It was found that the ultrasound-assisted synthesis method showed a faster increase in luminance and shorter induction time than the solvothermal method. The slope of the luminance increase during the transient period was also found to become increase with the addition of ultrasound, which also affects the growth of particles. Observation of the aliquoted reaction solution confirmed that particle growth was faster in the ultrasound-assisted synthesis method than in the solvothermal method. Numerical simulations were also performed using MATLAB ver. 5.5 to analyze the unique reaction field generated by ultrasound. Bubble radius and temperature inside a cavitation bubble was obtained using the Keller-Miksis equation, which reproduces the motion of a single bubble. The bubble radius expanded and contracted repeatedly according to the ultrasound sound pressure, and eventually collapsed. The temperature at the time of collapse was extremely high, exceeding 17,000 K. It was confirmed that the high-temperature reaction field generated by ultrasound irradiation promoted nucleation, leading to a reduction in particle size and induction time.

Correcting the hebbian mistake: Toward a fully error-driven hippocampus.

The hippocampus plays a critical role in the rapid learning of new episodic memories. Many computational models propose that the hippocampus is an autoassociator that relies on Hebbian learning (i.e., "cells that fire together, wire together"). However, Hebbian learning is computationally suboptimal as it does not learn in a way that is driven toward, and limited by, the objective of achieving effective retrieval. Thus, Hebbian learning results in more interference and a lower overall capacity. Our previous computational models have utilized a powerful, biologically plausible form of error-driven learning in hippocampal CA1 and entorhinal cortex (EC) (functioning as a sparse autoencoder) by contrasting local activity states at different phases in the theta cycle. Based on specific neural data and a recent abstract computational model, we propose a new model called Theremin (Total Hippocampal ERror MINimization) that extends error-driven learning to area CA3-the mnemonic heart of the hippocampal system. In the model, CA3 responds to the EC monosynaptic input prior to the EC disynaptic input through dentate gyrus (DG), giving rise to a temporal difference between these two activation states, which drives error-driven learning in the EC→CA3 and CA3↔CA3 projections. In effect, DG serves as a teacher to CA3, correcting its patterns into more pattern-separated ones, thereby reducing interference. Results showed that Theremin, compared with our original Hebbian-based model, has significantly increased capacity and learning speed. The model makes several novel predictions that can be tested in future studies.

Retrieval stopping can reduce distress from aversive memories.

Aversive memories have the potential to impair one's psychological well-being. It is desirable to reduce the anguish over such memories, as well as the chance that they will be retrieved. In two experiments, we investigated whether retrieval stopping reduces the distress elicited by negative memories retrieved from cues and how the effects of retrieval stopping are modulated by mental disorders, such as depression and anxiety. Participants engaged in retrieval stopping of aversive scene memories without any diversionary thoughts (direct suppression, Experiment 1) or with diversionary positive thoughts (thought substitution, Experiment 2). Direct suppression reduced arousal elicited by the retrieval of aversive memories, while thought substitution did not only reduce arousal but also increased positive valence. Self-reported anxious/depressive symptoms negatively modulated the effects of direct suppression. For no or mild anxious/depressed individuals, direct suppression alleviated negative valence and high arousal when retrieving aversive memories. The negative relationship was not observed between the severity of the symptoms and the effect of thought substitution. These findings suggest that both retrieval stopping strategies can reduce distress from aversive memories.

Effect of geometrical configuration of reactor on a ZrP nano-dispersion process using ultrasonic irradiation.

This study investigated the position of ultrasonic irradiation source and reactor geometry on fragmentation rate of a layered compound, α-zirconium phosphate (α-ZrP). By numerically solving the acoustic pressure distribution using COMSOL Multiphysics®, it is clarified the mechanism whereby the operating factors influenced the α-ZrP dispersion to make a suggestion of guideline of the process design method. Two vessels made of glass with a flat-bottom and a spherical-bottom, respectively, were used. Although the flat-bottom vessel at lower horn position showed the best performance of fragmentation, the region of high acoustic pressure field in the flat bottom vessel sharply narrowed and the transmittance became prominently low. On the other hand, no significant difference of the transmittance value in the spherical bottom vessel between the cases of low and high horn positions could be observed and the spherical bottom vessel was robust for the horn position. These results suggest that not only the magnitude of acoustic pressure but also the size of high acoustic pressure region is also an important factor and a spherical bottom vessel is one of suitable shape which gives large size of high acoustic pressure region regardless of the horn position.

Axopodial degradation in the heliozoon Raphidiophrys contractilis: a novel bioassay system for detecting heavy metal toxicity in an aquatic environment.

We observed the physiological effects of zinc, lead, mercury, copper, cadmium, and arsenic on the axopodia of the centrohelid heliozoon Raphidiophrys contractilis. In the presence of these heavy metal ions, the axopodial length of the heliozoon decreased in a concentration-dependent manner. When the heavy metal ions were examined at the same concentration, mercury produced the strongest effect on axopodia. At a high concentration (> 10-3 M) of any of the heavy metal ions examined, axopodia disappeared and cells became disrupted. Axopodia were also degraded by the addition of solutions with an acidic (< or = 6) or basic (> or = 8) pH. These observations indicate the toxic effects of heavy metal ions and non-neutral pHs on axopodial length, and also signify that R. contractilis can be used as an effective biological tool for the study of metal poisoning in eukaryotic cells.